Under a communication environment between a motor drive control apparatus and a position information detector, if a rate of occurrence of communication abnormality is high, a motor could stop. Therefore, communication speed could be changed according to the rate of occurrence of communication abnormality.
For example, as a control method for changing communication speed according to a rate of occurrence of communication abnormality for the purpose of securing communication reliability, there is a technology disclosed in Patent Literature 1. In the technology disclosed in Patent Literature 1, the number of times of communication abnormality is counted under a communication environment in which communication abnormality occurs and, when the number of times of abnormality reaches a certain threshold, communication speed is changed, whereby communication reliability is always secured.